I just read an artcle on the Windows Secrets site about a test a guy did where he installed the 20 most popular programs from cnet and then uninstalled them. They slowed down the boot up time of his computer a lot even after being uninstalled.
He used three different cleaner utilities to try to help the situation and they all worked quite well.
so, for future reference, here's a short how-to.
He used CCleaner’s file and Registry cleanup routines in their default settings and it worked.
Without even downloading anything, you can use Windows cleanmgr to cleanup. Click Start, type cmd and click the icon to start a DOS prompt. Type cleanmgr and enter. This should run the Disk Cleanup util. You get more functionality if you start it this way. You should be able to delete most of the items on the list that Disk Cleanup gives you. I uncheck Hibernation, Recycle Bin (I sometimes have things in there I end up needing), and setup log files (useful -for me- diagnostics in there)
There are also two uninstall programs you can use to clean up. Revo Uninstaller, and there is a Microsoft Fix-It that will help uninstall crap at http://support.microsoft.com/mats/Program_Install_and_Uninstall
I've used the Revo Uninstaller in situations where the Add Remove Programs control panel applet is blank. I was able to remove programs even though the Add Remove Programs wouldn't work.
Microsoft used to offer the Windows Installer CleanUp Utility, which can still be found for download if you search. I found it on the MajorGeeks website. But this utility is no longer compatible with current versions of Office. But I've used the utility to uninstall other programs, like the remnants of the VZAccess Manager for Verizon Wireless data connections, and the drivers for the tethered device.